2.0 Analysis 2.1 Flight Crew Training and Qualifications The flight crew was properly qualified, trained, and experienced, and had consistently demonstrated high levels of performance during Transport Canada flight evaluations. There was no evidence of pre-existing medical conditions which would have incapacitated either crew member. 2.2 Meadow Lake Circling Approach Both crew members were familiar with the Meadow Lake aerodrome and with the company- approved circling approach. The crew had received a weather briefing prior to the flight, as well as radio updates from Cold Lake and from the AES observer at Meadow Lake, and they were aware that the reported ceiling at the Meadow Lake aerodrome was 500 feet agl, and was below the category D circling limits. Although weather conditions in the vicinity of Meadow Lake were conducive to the formation of airframe and airfoil icing, no evidence of ice was found on the aircraft. The crew reportedly had no overriding pressure to complete this flight under unsuitable weather conditions. The reason why they initiated the flight, and why they attempted the approach under the reported weather conditions was not determined. The aircraft was visible to observers on the ground as it passed over the Meadow Lake terminal building, and therefore must have been at or below the measured cloud base of 400 feet agl at the time of the accident; the aircraft appeared to be circling to land on runway 26. No definitive reason could be found to explain why the aircraft was manoeuvring below the category D MDA of 604 feet agl during the circling manoeuvre. Even if the crew had obtained visual contact with the ground at the category D MDA, the recommended practice is to remain at the circling MDA until a normal landing is assured. The aircraft's speed at the time of the abrupt in-flight manoeuvring was calculated to be between 129 and 154 KIAS. Based on these calculations, it appears that the aircraft may have been manoeuvring at or below its normal circling approach speed. The risk inherent in flying at a lower airspeed is that the buffer between the aircraft's actual manoeuvring speed and its stall speed will be reduced. Extra precautions will then be necessary to limit the flight loading during any turning manoeuvres and to prevent a stall. 2.3 Abrupt In-Flight Manoeuvres The aircraft was executing a left-hand turn to line up with runway 26 when it completed a number of rapid-onset, steep-banked, rolling manoeuvres. The event was of short duration, lasting only a few seconds. Based on the witnesses' descriptions, it is possible that the aircraft was also subjected to a negative g force while it was established in a steep right-banked attitude. The cause of these manoeuvres could not be determined, but the manoeuvres were likely associated with an accelerated stall. 2.3.1 Aircraft Position at the time of the Manoeuvres At the time of the observed manoeuvres, the aircraft was turning back toward the runway and would have normally been established in a left-hand, 30-banked turn. However, the circling procedure had been initiated overhead the aerodrome, and a westerly wind would have caused the aircraft to drift even further toward the east, to a point approximately 2.5 nm away from the aerodrome's runway environment and outside the obstacle clearance areas for the circling approach. This placed the aircraft in the vicinity of a 200-foot radio broadcast tower. Since the captain was familiar with this tower's location, it is likely that the crew recognized they were in its vicinity; this may have prompted the crew to tighten the turn back toward the aerodrome. 2.4 Possible Explanations for the Abrupt Manoeuvres 2.4.1 Possibility of an Accelerated Stall With the aircraft's C of G at the aft limit, there would be an increased probability that the aircraft might over-rotate with the application of up-elevator. The aft C of G would have reduced the aircraft's pitch stability, and increased the probability of an accelerated stall. Based on one witness's description of the abrupt manoeuvres that were observed prior to impact, it is possible that the aircraft may have been subjected to a negative g force while in a steep, right-banked attitude. If that were the case, then the rolling manoeuvre may have been caused by a high-speed stall, and the nose movement to the left, as observed by the witness, may have been the result of the crew's control input to recover from that stall. 2.4.2 Possibility of a Planned and Intentional Manoeuvre It is possible, however, that the in-flight manoeuvres observed by the witnesses may have been planned and intentionally actioned by the crew in order to situate the aircraft with respect to both the radio tower and the airport. However, it is unlikely that a professional flight crew would undertake such abrupt manoeuvres at low altitude and with degraded visual references, as the risk would increase significantly. 2.4.3 Possibility of an Undetermined System Malfunction There was no indication of any pre-impact aircraft failure or system malfunction that would have caused the abrupt in-flight manoeuvring, nor was there any indication of an in-flight fire. At impact, the aircraft configuration was consistent with the circling approach. All airfoil sections were accounted for and were in their appropriate positions for the phase of flight. The speed brakes, lift dumpers, and thrust reversers were all STOWED at impact, and the flaps were extended symmetrically at 20. Based on the observed flight dynamics, it is unlikely that a transient deployment of any of these ancillary control systems occurred prior to or during the abrupt in-flight manoeuvring. 2.5 Loss of Altitude Control Regardless of the underlying cause, the steep-banked attitude and abrupt manoeuvres resulted in a loss of altitude control and the aircraft began an approximately 8 descent path to impact. During the descent, it appears that the flight path was directionally stable. The aircraft hit the ground with a velocity of 175 KIAS and with a vertical velocity of approximately 2,200 fpm. The aircraft was in an approximately 15 nose-up, slightly right-wing-low attitude at impact, which suggests that one or both of the crew members had recognized the altitude loss and was attempting to initiate an overshoot procedure. Because the time between the observed manoeuvres and the impact was of short duration, it is unlikely that the crew had sufficient time to recognize the situation, initiate the appropriate response, and complete the recovery before striking the ground. The crew's ability to judge altitude and flight path angle by visual means may have been adversely affected by the whiteout conditions that were present, which would likely have slowed their recovery response. 3.0 Conclusions 3.1 Findings Both crew members held valid Airline Transport Pilot Licences, valid instrument endorsements, and current pilot proficiency checks. The aircraft was maintained in accordance with the approved maintenance schedule and was certified as being airworthy prior to the flight. The aircraft was not equipped with a flight data recorder or a cockpit voice recorder, nor was either required by regulation. Although the aircraft's weight and balance were within the prescribed limits, the aircraft's C of G was at the aft limit of the C of G operating range. The aft C of G condition would have reduced the aircraft's pitch stability, increased its susceptibility to aerodynamic stall, and aggravated its stall characteristics. Wind conditions at Meadow Lake required the crew to complete the NDB approach to runway 08, then perform a circling procedure to land on runway 26. The normal approach speed of 150 KIAS required that the crew carry the circling procedure down to the category D MDA of 604 feet agl. The measured ceiling of 400 feet did not allow the circling procedure to be conducted at category D minima. The aircraft passed over the Meadow Lake terminal building at or below the cloud base of 400 feet agl and appeared to be circling to land on runway 26 at an altitude lower than the published category D circling minima. The aircraft manoeuvred approximately 2.5 miles from the runway environment, and was outside the category D obstacle clearance area for the final portion of the flight. It is likely that the crew recognized they were outside the normal manoeuvring area and tightened the turn while turning back toward the aerodrome. The aircraft entered a number of steep-banked rolling manoeuvres while turning to line up with runway 26 at Meadow Lake. Following the abrupt in-flight manoeuvring, pitch and roll control were re-established prior to impact; the aircraft struck the ground in a nose-high, slightly right-wing-low attitude, suggesting that recovery was initiated. Both engines were producing power at impact; however, the extent of engine power could not be established. It is unlikely that the crew had sufficient time to complete the recovery. Although weather conditions in the vicinity of Meadow Lake were conducive to the formation of airframe and airfoil icing, no evidence of ice was found on the aircraft. The crew's ability to judge altitude and flight path angle by visual means may have been adversely affected by the whiteout conditions that were present, and this would likely have slowed their recovery response. There was no evidence of pre-existing medical conditions which could have incapacitated either crew member. There was no evidence of any pre-impact aircraft system failures that could have caused the abrupt in-flight manoeuvring, nor was there any evidence of an in-flight fire. The accident was considered to be non-survivable because of the magnitude of the deceleration forces, and the subsequent thermal stress. 3.2 Causes While circling to land on runway 26, the aircraft performed a non-typical circling procedure at a lower than published circling altitude, leading to loss of control consistent with an accelerated stall, and descended into terrain before recovery could be completed. Whiteout conditions may have contributed to this occurrence. The Board has no aviation safety recommendations to issue at this time.4.0 Safety Action The Board has no aviation safety recommendations to issue at this time.